Ive just done my motorcycle hazard perception test. Not sure if its the same for cars. I found it better to click 2 or 3 times when you first see the hazard. On the dvd i often reacted too quickly to register 5 points which i found a bit strange personally. After a bit of practice i found that you often had to click 2 or 3 times to ensure you register a good score (4 or 5 points).

Be careful though, if you click too many times you get a no score. I did this once on my actual test as i was a bit over cautious and clicked for every little thing.

Some of them were quite hard and you had to look way into the distance to get 4 or 5.